Apparatus and associated method for communicating multimedia information upon a communication link

ABSTRACT

Apparatus, and associated method, converts real-time multimedia information generated pursuant to an RTP protocol into a form amenable for transmission upon a radio channel, such as a radio channel defined in a cellular communication system. When converted, the informational content of the multimedia information is transmitted in a manner that achieves spectral efficiency and low, constant delay. Once transmitted over the radio channel, the multimedia information is converted back into form corresponding to the RTP protocol before being sent to the receiving station.

The present application is a continuation of U.S. patent applicationSer. No. 09/283,808, filed on Apr. 1, 1999 now U.S. Pat. No. 6,466,585.

The present invention relates generally to the communication ofmultimedia information, such as multimedia information formattedpursuant to the RealTime Transport Protocol (RTP). More particularly,the present invention relates to apparatus, and an associated method,for converting realtime multimedia information, formatted in packet dataform, such as that formatted pursuant to the RTP, into a form tofacilitate transmission of the information on a radio channel. Operationof an embodiment of the present invention permits the communication ofmultimedia information by way of a cellular, or other radiocommunication system, with minimal and constant time delay while alsocommunicating the information in a spectrally-efficient manner.

BACKGROUND OF THE INVENTION

Advancements in communication technologies have permitted theintroduction of, and popularization of, new types of, and improvementsin existing, communication systems. Increasingly large amounts of dataare permitted to be communicated at increasing thruput rates through theuse of such new, or improved, communication systems. As a result of suchimprovements, new types of communications, requiring high data thruputrates, are possible. Digital communication techniques, for instance, areincreasingly utilized in communication systems to efficientlycommunicate digital data, and the use of such techniques has facilitatedthe increased data thruput rates.

Multimedia communications, for instance, are exemplary of new types ofcommunications permitted as a result of the improvements incommunications technologies. Multimedia communications refer, generally,to the communication of more than one type of data between a sendingstation and a receiving station. Typically, the communication of suchmore than one type of data appears, to a user, to be simultaneous.Multimedia communications include, for instance, voice-over-dataapplications. Audio signals overlaid upon video signals used toeffectuate teleconferencing is an example of a multimedia communicationapplication. Two-way white board communication is exemplary of anothermultimedia communication application.

The different types of data exhibit different communicationrequirements. For instance, voice data must be communicated inreal-time. That is to say, voice data must be communicated withoutsignificant delay and must be communicated in a manner which permits itsreconstruction at a receiving station in a manner which introducesminimal time distortion. Otherwise, the voice data shall appear to benoticeably distorted. Conversely, non-voice data is not astime-sensitive. However, more stringent accuracy requirements areassociated with non-voice data.

Multimedia communications can be effectuated utilizing packet datacommunication techniques. With the popularization of the Internet andcommunication thereon, standardized, multimedia protocols have been setforth by which to communicate multimedia information in a form amenableto its transmission by way of the Internet. An example of multimediaprotocol is H.323. H.323 is a widely used ITU standard which uses RTP.

According to the H.323 protocol, when multimedia data is to betransmitted by a sending station, logical channels upon which totransmit the data are assigned. The data channels are allocatedresponsive to requests made by the sending station. Separate logicalchannels are requested for separate types of data. For instance, a firstlogical channel is requested upon which to transmit voice data, andallocation of a second logical channel is requested for transmission ofnon-voice data. A subset of the H.323 protocol, referred to as the H.245protocol, defines the manner in which the channels are requested.Packets of data are thereafter transmitted upon the logical channels. Inconventional manner, the individual packets include header information,such as IP, UDP and RTP information, to identify to where the packet isto be directed and to provide a time stamp with the packet. Theinformation of a packet of data, referred to as the payload, is appendedto the header information.

The H.323 protocol was intended originally for wireline communications,such as between communication stations, connected by wirelineconnections including those of the Internet. But, advancements incommunication technologies have also permitted the widespread usage ofradio communication systems. A cellular communication system isexemplary of a wireless communication system which has achieved widelevels of popularity and usage. Telephonic communication by way of acellular communication system mimics communication by way of aconventional wireline, telephonic system. However, because a radio-linkis utilized in a cellular, or other radio, communication system,bandwidth considerations are generally more significant than whenwireline networks are utilized for communications. That is to say, theradio-link upon which communication is communicated in a radiocommunication system is of a limited bandwidth capacity. And, byreducing the bandwidth requirements of information communicated thereon,the information capacity of the radio-link can be increased. So, effortsare made to minimize the bandwidth requirements of signals transmittedover the radio-link.

Information communicated pursuant to an H.323 protocol is predicatedupon a packet-data configuration. The header information required ofeach packet of data is relatively bandwidth-consumptive. As a result,communication of multimedia information by way of a radio-link, such asthat formed in the operation of a cellular communication system, is arelatively inefficient manner by which to communicate multimediainformation. However, because the RTP-based protocol has become a defacto standard by which to format multimedia information, multimediastations shall likely continue to be operable pursuant to such protocolirrespective of the bandwidth inefficiency of communication of packetdata by way of the radio-link.

If a manner could be provided by which more efficiently to communicatemultimedia information by way of a radio-link, while still utilizing theRTP-based protocol at the sending and receiving stations, improvedmultimedia communications by way of a radio communication system couldresult.

It is in light of this background information related to multimediacommunications that the significant improvements of the presentinvention have evolved.

SUMMARY OF THE INVENTION

The present invention, accordingly, advantageously provides apparatus,and an associated method, for converting real-time multimediainformation formatted in packet-data form, into a form to facilitatetransmission of the information on a radio channel. Through suchconversion, the multimedia information can be transmitted with minimaltime delay while also being transmitted upon the radio channel in aspectrally efficient manner.

In one aspect of the present invention, real-time media, which is partof multimedia information, is communicated between sending and receivingmultimedia stations. On the communications path between the sending andreceiving stations there is a communications link, such as a radio link,that has bandwidth limitations and spectrum efficiency requirements. Inwhat follows, that link shall, at times, be referred to as thecommunications link. The multimedia information, when generated at asending multimedia station, and when provided to a receiving multimediastation, is formatted in packet-data form according to an existing RTPprotocol. Before transmission on the communications link, real-timemedia is converted into a communications-link format. Once convertedinto the communications-link format, the real-time media can betransmitted upon a special channel on the communications-link in anefficient manner. Once received, the real-time media is converted out ofthe communications-link format and back into the packet-data formatbefore being sent to the receiving station. The same process takes placein the reverse direction. A special channel is defined as a channel thatprovides a constant bit rate. In a CDMA (code-division, multiple-access)communication system, the channel can be realized by a unique code bywhich the information to be communicated is encoded. In a TDMA(time-division, multiple-access) communication system, the channel canbe realized by a time slot-frequency combination. Other ways to realizea special channel are possible.

A typical example of communications link is a radio link.

Consider the example of a cellular multimedia station communicating witha wireline multimedia station. At the cellular station, the outgoingmultimedia information is converted into a radio-link format. Onceconverted into the radio-link format, the multimedia information can betransmitted upon the radio-link in an efficient manner. Once received,the multimedia information is converted out of the radio-link format andback into the packet-data format before being sent to the wirelinestation. The reverse process takes place in the reverse direction.

In one implementation, the multimedia stations include multimediaterminals. The multimedia terminals are operable to generate, and toreceive, multimedia information formatted pursuant to a multimediaprotocol such as H.323. Multimedia information is communicated betweenthe multimedia terminals by way of a radio communication system, such asa cellular communication system.

Operation of an embodiment of the present invention converts the packetdata-formatted information into a form to permit its efficienttransmission upon a channel defined in the cellular communicationsystem. The multimedia protocol provides for two components, a controlplane and a user plane. The control plane includes an applicationsignaling protocol, such as H.245 for H.323. The application signalingprotocol specifies logical channels to be opened for the communicationof the different types of multimedia information. Operation of anembodiment of the present invention monitors the application signalingand detects the opening and closing of logical channels defined in thecontrol plane. Messaging to open a real-time media channel is translatedinto messaging to set up a special channel upon which to communicatemultimedia information between the multimedia stations. Monitoringcontinues, and when the application signaling indicates that the logicalchannels are to be closed, the corresponding special channel is alsoclosed.

As the multimedia protocol such as H.323 is increasingly being used inInternet Protocol (IP)-based communication systems to effectuatemultimedia communications, operation of an embodiment of the presentinvention advantageously permits multimedia devices, operable pursuantto the protocol, to operate without alteration. Apparatus of anembodiment of the present invention monitors signals generated by suchexisting multimedia devices, and utilizes such signals to convert themultimedia information into a form more amenable for transmission upon acircuit-switched, or other, radio channel. Overhead data, such as IP,RTP and UDP headers associated with each packet of data, is removedprior to transmission of the multimedia information upon the specialchannel. Subsequent to transmission upon the special channel, multimediainformation is reconverted back into packet-data format, and the headerinformation is affixed again to the packets of data. Because the headerinformation, otherwise forming a portion of each packet of data, isremoved prior to transmission of the payload data, the same informationis not repeatedly transmitted on the special channel. Improved spectrumefficiency results.

In these and other aspects, therefore, apparatus, and an associatedmethod, is provided for converting packet-formatted multimediainformation into a radio-link format. Once converted into the radio-linkformat, the multimedia information is amenable for transmission upon aradio-link extending between a first communication station and a secondcommunication station of a radio communication system. A detector iscoupled to receive indications of the packet-formatted data. Thedetector detects control plane information associated with thepacket-formatted data. A requester is coupled to receive indications ofdetection by the detector of the control plane information. Therequester requests allocation of a special channel defined by theradio-link extending between the first and second communicationstations, respectively, for communication of the multimedia informationthereon. A format converter is coupled to receive the packet-formatteddata of which the multimedia information is formed. Responsive toallocation of the special channel requested by the requester, the formatconverter converts the packet-formatted data into the radio-link format.Thereafter, transmission of the multimedia information, formatted in theradio-link format, is permitted upon the special channel.

A more complete appreciation of the present invention and the scopethereof can be obtained from the accompanying drawings which are brieflysummarized below, the following detailed description of thepresently-preferred embodiments of the invention and the appendedclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a functional block diagram of a radio communicationsystem operable pursuant to an embodiment of the present invention tocommunicate multimedia information.

FIG. 2 illustrates a functional block diagram of the control plane ofthe radio communication system shown in FIG. 1 constructed according toan embodiment of the present invention.

FIG. 3 illustrates a functional block diagram of the user plane of theradio communication system shown in FIG. 1 according to an embodiment ofthe present invention.

FIG. 4 illustrates a functional block diagram, similar to that shown inFIG. 2, but according to another embodiment of the present invention.

FIG. 5 illustrates a functional block diagram similar to that shown inFIG. 3, but according to another embodiment of the present invention.

FIG. 6 illustrates the format of multimedia information generated duringoperation of an embodiment of the present invention.

FIG. 7 illustrates a functional block diagram of a portion of a radiocommunication system, here to illustrate operation of an embodiment ofthe present invention during hand-off procedures.

FIG. 8 illustrates a functional block diagram of a further embodiment ofthe present invention.

FIG. 9 illustrates a method flow diagram listing the method steps of themethod of operation of an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Turning first to FIG. 1, a radio communication system, shown generallyat 10, is operable to communicate multimedia information betweenmultimedia stations. In the Figure, exemplary multimedia stations 12 and14 are shown. In the exemplary implementation, the radio communicationsystem 10 comprises a cellular communication system, such as a CDMA orTDMA communication system. In other implementations, the radiocommunication system is formed of other types of radio communicationsystems.

Multimedia information is communicated between the multimedia station 12and the infrastructure by way of forward and reverse link channels, hererepresented by the arrows 16 and 18. In an implementation in which theradio communication system is formed of a CDMA cellular communicationsystem, the forward and reverse link channels are defined by uniquecodes by which signals are encoded prior to their transmission. And,when the radio communication system comprises a TDMA, cellularcommunication system, the forward and reverse channels are defined bytime slot-frequency combinations. In other implementations, the channelsare defined in other manners.

The multimedia station 12 is here shown to include a multimedia device22 and a mobile station 24. It should be understood, of course, that theembodiment shown in the figure is exemplary. In other implementations,the mobile multimedia station is constructed in other manners. Themultimedia device 22 is operable to generate and receive real-timemultimedia information pursuant to a packet data format such as the RTPprotocol. In what follows, multimedia information generated by themultimedia device 22 will at times be referred to as mobile originated(MO), while multimedia information received by 22 will at times bereferred to as mobile terminated (MT). In conventional manner, MOmultimedia information is formatted into packets of data at themultimedia device 22. In one implementation, the packet-formatted datais converted, at the multimedia device, into a form more amenable to itstransmission upon the reverse radio-link. The form will at times bereferred to as radio-link format.

The mobile station 24 here forms a cellular radio telephone operable ina cellular communication system and is capable of transceiving signalson the forward and reverse link channels 16 and 18. The mobile station24 is here shown to be coupled to the multimedia device 22 by way oflines 26. MO multimedia information is provided to the mobile station 24therethrough. As noted above, in one implementation, the MOpacket-formatted multimedia information is converted into a radio-linkformat at the multimedia device 22. In another implementation, suchconversion is performed at the mobile station 24. MT multimediainformation transmitted upon a forward link channel and received at themobile station 24 is analogously also convertible out of a radio-linkformat and into packet-data format, either at the mobile station 24, orat the multimedia device 22, depending upon the manner in which thepresent invention is implemented.

The multimedia station 14 is here shown to be a fixed multimediastation, coupled to access network infrastructure 34 of a cellularcommunication system. Analogous to the multimedia station 12, themultimedia station 14 is operable to generate and receive the multimediainformation formatted pursuant to a packet data format such as the RTPprotocol. MT multimedia information is generated by 14 in packet dataformat. In one implementation, the access network infrastructure 34 isfurther operable to convert the packet-data formatted information into aradio-link format to facilitate efficient transmission of the MTmultimedia information upon the forward radio-link to the multimediastation 12. MO multimedia information, received in radio link format, isconverted by the access network infrastructure into packet data format.

The cellular system network infrastructure 34 is coupled to receive themultimedia information formed by the multimedia station 14 here by wayof the lines 36. While not separately shown, the multimedia station 14is coupled to the infrastructure 34 by way of an IP network. Theinfrastructure can also include elements based on GPRS (General PacketRadio Service). And, also while not separately shown, the infrastructure34 includes, base station controllers, and base transceiver stations.The infrastructure 34 is operable to transceive signals on the forwardand reverse channels, here represented by the arrows 16 and 18.

Associated with the user plane is the control plane. While the userplane relates to the packet data formatted multimedia informationdescribed above, the control plane relates to the protocols used forexample to establish and tear down the multimedia call, as well as thelogical channels carrying the individual media within the call. Forexample, the user plane of H.323 is based on RTP, while the controlplane includes various application signaling protocols, especiallyH.245. The conversion to a radio-link format by 24 and 34 of the MO andMT real-time multimedia information respectively, is predicated on theknowledge that the media is real-time. The knowledge is acquired by adetection function which monitors the application signaling exchanged inthe control plane. The detection function can be located in 24. Since 24does not alter the application signaling exchanged between 22 and 14,the control plane protocols of 22 can be conventional in nature.Furthermore, because operation of an embodiment of the present inventionconverts packet data-formatted information into a radio-link formatprior to its transmission and thereafter reconverts the information inthe radio-link format back to a packet-data format, the multimediadevice 22 can be of conventional construction in the user plane as well.That is to say, the multimedia device 22 can be of conventionalconstruction to generate multimedia information pursuant to a standardmultimedia protocol such as H.323. And, because of the conversion of theinformation into a radio-link format, the multimedia information can betransmitted in a spectrally efficient fashion upon a radio-link, such asthat defined in a cellular communication system.

FIG. 2 illustrates the logical layers of the control plane of the radiocommunication system 10 shown in FIG. 1 according to an embodiment ofthe present invention. The embodiment illustrated in FIG. 2 is that of anon-integrated configuration. That is to say, the embodiment shown inFIG. 2 is that of an implementation in which the upper logical layers ofthe control plane are conventional in nature, such as the upper levellayers of a laptop computer, or the like, which is operable pursuant toa multimedia protocol using RTP. such as H.323, in conventional manner,without alteration. In the illustration of FIG. 2, the stations 12 and14 and the access network infrastructure are pictured in terms ofapplication layers. Operation of the embodiment of the present inventionshown in the Figure adapts the multimedia protocol so that real-timemedia can be carried over a special air interface channel in a mannerbetter to meet the delay and spectrum efficiency requirements of a radiocommunication system.

The forward and reverse channels 16 and 18 are commonly designated inthe Figure. When the cellular communication system comprises a CDMAcellular communication system, such as that described in the IS-95standard promulgated by the EIA/TIA, dedicated codes are used by whichto encode the information prior to its transmission. And, in a TDMAcellular communication system, such as that defined in the IS-136standard promulgated by the EIA/TIA, dedicated time slot-frequencycombinations define the channels.

Here, the multimedia station 12 is shown to include an applicationsignaling layer 48. The application signaling layer is defined pursuantto the multimedia protocol. For example, H.245 is the applicationsignaling corresponding to the H.323 multimedia protocol. The layer 48is operable, amongst other things, to request logical channels uponwhich to communicate different types of multimedia information. Forinstance, a request is made to open a logical channel to communicatevoice data, or to communicate non-voice data, etc. Subsequent tocommunication of the data, a request is made to close the logicalchannel.

Signaling generated by the layer 48 is provided to a TCP layer 50 whichis operable to form TCP data segments. The TCP layer runs on an IP layer52 which is operable to format the data segments according to the IPprotocols to add, e.g., headers and trailer thereto.

Formatted data generated by the layer 52 is detected by an adaptationlayer 54. The adaptation layer 54 is here shown to perform, amongstother things, detection of the signaling generated by the upper layers.Here the function of the adaptation layer 54 to detect the data isrepresented by a detector 56. Responsive to detection of data generatedby the layer 52, the adaptation layer 54 translates such signaling intoa request to set up a special channel upon the radio-link extendingbetween the stations 12 and the access network infrastructure. Suchfunction performed by the adaptation layer 54 is represented in theFigure by a requester 58.

The access network infrastructure 34 is here shown also to include lowerlayers 68 which correspond to the lower application layers 66 of themultimedia station 12.

The access network infrastructure 34 further includes additional lowerlayers 76 to carry the application signaling. The lower layers 76permits formation of a link by way of an IP backbone 78 with lowerlayers 82 of the station 14. The access network infrastructure isfurther shown to include a real-time manager 84.

Analogous to the layers 48, 50, and 52 of the station 12, the station 14includes an application signaling layer 88, a TCP layer 90, and an IPlayer 92. The application signaling layer 88 is defined pursuant to themultimedia protocol and is operable, amongst other things, to requestlogical channels upon which to communication different types ofmultimedia information. The TCP layer 90 is operable to form, and toreceive, TCP data segments. And, the IP layer 92 is operable to formatdata segments, and to strip formatted data segments, in conventionalmanner. In such manner, both the stations 12 and 14 are formed of, inpart, regular multimedia protocol over IP devices. That is to say, IPpacket-formatted information, formatted pursuant to a multimediaprotocol can be received, and generated thereat.

In exemplary operation in which the station 12 initiates communications,a request to set up a special channel is generated and provided, by wayof the various layers 12, the radio links 16–18, the various layers ofthe access network infrastructure, and provided to and processed at thereal-time manager 84 of the access network infrastructure. Setting up ofthe special channel includes setting up the channel on the radio link aswell as converter functions (described below) in a user plane (alsodescribed below). After successful processing, a special channel isavailable to carry real-time media. The requester exchanges signalingwith the real-time manager 84 over the paths labeled (4) and (4′) inFIG. 2. In addition, H.245 (H.323 application signaling) exchangedbetween the station 12 and a remote end point, here the station 14, isrelayed by the access network infrastructure over the paths labeled (2)and (2′) in the Figure.

FIG. 3 again illustrates the radio communication system 10 shown inFIGS. 1–2, again showing multimedia stations 12 and 14 and accessnetwork infrastructure 34. FIG. 3 illustrates the user plane of anon-integrated configuration, analogous to the control plane layers ofthe non-integrated configuration shown in FIG. 2.

Here, the station 12 includes a real-time media layer 102 which runs ontop of a RTP layer 104. The RTP layer is operable, amongst other things,to add a time stamp to data segments generated by the real-time medialayer 102. The time stamp specifies the time when the associatedreal-time media sample was generated. The time stamp is used by thereceiving end to correct any delay fluctuation introduced by the IPbackbone network. The RTP layer also adds a sequence number to eachpacket. The sequence number is used by the receiving end to detectpacket loss and/or missequencing and take the appropriate correctiveaction. The RTP header also includes other information, such as theSynchronization Source (SSRC). All packets coming from a SSRC are partof the same timing and sequence number space.

The RTP layer 104 runs on top of a UDP layer 106 which is operable toformat data segments applied thereto. The UDP layer 106 runs upon an IPlayer 108. The IP layer 108 corresponds to the IP layer 52 shown in FIG.2. The IP layer runs upon the adaptation layer 54 which here is operableto perform converting functions, represented by the converter 112.Again, the adaptation layer runs upon lower layers, here againrepresented by lower layers 66.

A special channel 114 forms during operation of an embodiment of thepresent invention interconnects the station 12 with the access networkinfrastructure 34. As shown, the special channel interconnects the lowerlayers 66 of the station 12 with corresponding lower layers 68 of theaccess network infrastructure. The infrastructure 34 is here shown toinclude an access network infrastructure converter 116 which runs uponthe lower layers 68. The converter 116 is also shown to run upon lowerlayers 76, which also were shown previously in FIG. 2. The lower layers76 are connected by way of the IP backbone 78 with the correspondinglower layers 82 of the station 14.

The station 14 is here shown to include layers 122, 124, 126 and 128which correspond with the corresponding layers 102, 104, 106, and 108,respectively, of the multimedia station 12.

During operation of the radio communication system, when in the userplane, packetized real-time media generated by the multimedia station 12is processed by the converter 112. The converter 112 removes the RTP,UDP, and IP headers attached to the media generated by the medial 102 atthe layers 104, 106, and 108, respectively. Once removed, the resultantmedia is provided to the lower layers 66.

The lower layers 66 are operable to perform conventional lower layerfunctions. For example, if real-time media is speech, lower layers mayperform convolutional coding, interleaving, etc. They may also performmultiplexing with other types of traffic and media. As a result ofprocessing by the converter, real-time media is transmitted in aspectrally efficient manner upon a radio link formed of the specialchannel 114. At the access network infrastructure, lower layers 68perform the inverse operations. Thereafter, the converter 116regenerates the RTP, UDP and IP headers. As the values of the UDP and IPfields do not change during a call, their values need only to be sent tothe access network infrastructureat the special channel set up time andat time of handoff to another converter.

As the values of the RTP fields change, the ANI (Access NetworkInfrastructure) converter 116 must be able to derive the correct timestamps and sequence numbers of the RTP field. In one implementation, inwhich a circuit switched mode is used for the special channel, real-timemedia is received by the converter 116 in an extremely predictablemanner. Therefore, the converter 116 is able to derive the runningvalues of the RTP time stamp and sequence numbers merely by maintaininga local clock that increments monotonically and linearly in time.

For real-time media originating at the station 14, the converter 16removes the RTP, UDP, and IP headers and generates a real-time mediastream with the timing defined by the time stamps and sequence numbersreceived from the station 14. The result is transmitted upon the specialchannel 114. The converter 112 regenerates the RTP, UDP and IP headersbased upon the same principle of a local clock.

Thereby, the mobile multimedia station 12, together with the ANIconverter 116, appears to the multimedia station 14 merely to be anotherconventional multimedia station. In spite of such appearance to themultimedia station 14, operation of an embodiment of the presentinvention converts such packet data-formatted information into aradio-link format to facilitate its transmission in a spectrallyefficient manner upon a radio-link. Once the radio-link-formattedinformation is received at the converter, the packet data-format of theinformation is regenerated.

FIG. 4 again illustrates the communication system 10, shown previouslyin FIG. 1, here again showing multimedia stations 12 and 14 and theaccess network infrastructure 34. Here, the logical layers of thecontrol plane operation are illustrated in which the logical layers areformed in an integrated configuration according to an embodiment of thepresent invention. In this implementation, modifications are made tovarious of the logical layers to facilitate efficient communication ofthe multimedia between the stations 12 and 14.

In this implementation, the station 12 is shown to include anapplication signaling layer 148 which runs directly upon an adaptationlayer 152 and also directly upon a TCP layer 154. Analogous to theadaptation layer 54 shown in the embodiment of FIGS. 2–3, the adaptationlayer performs requesting functions, represented by the requester 156.The requester 156 performs functions analogous to the requester 58 shownin FIG. 2. In this implementation, the adaptation layer 152 need notperform detection functions.

The TCP layer 154 runs upon an IP layer 158.

The radio link formed of the radio channels 16 and 18 are again picturedas a single line 16–18 in the Figure. The access network infrastructure34 is logically identical to that shown in the embodiment of FIG. 2.Here, the network infrastructure is shown to include lower layers 168,corresponding to the lower layers 68 shown in FIG. 2, and lower layers176 corresponding to the lower layers 76 shown in FIG. 2. The lowerlayers 176 are coupled by way of an IP backbone 178 with lower layers182 of the multimedia station 14. And, the network infrastructure 34 isagain shown to include a real-time manager 184, corresponding to thereal-time manager 84 shown in FIG. 2.

The multimedia station 14 is here shown include an application signalinglayer 188 which runs upon a TCP layer 190 which, in turn, runs upon anIP layer 192. The layers 188, 190 and 192, form the functions of thelayers 148, 154 and 158. respectively, of the multimedia station 12.

FIG. 5 illustrates the user plane logical layers of the communicationsystem 10 of the integrated configuration. Here, again, thecommunication system includes a multimedia station 12 and a multimediastation 14 together with an access network infrastructure 34. Once acall is established responsive to operation of the control planefunctions, multimedia information is communicated between the multimediastations 12 and 14 by way of the user plane.

The multimedia station 12 is here shown to include two logical layers,real-time media layer 202 and lower layers 166. A special channel 214 isformed to extend between the station 12 and the access networkinfrastructure 34. In the user plane, the access network infrastructureshown in FIG. 5 corresponds identically with the access networkinfrastructure logical layers shown in FIG. 3, here including lowerlayers 168 and access network infrastructure (ANI) converter 272, andlower layers 176.

The lower layers 176 are coupled by way of an IP backbone 178 with lowerlayers 182 of the multimedia station 14. The station 14 is further shownto include a real-time media layer 222, an RTP layer 224, a UDP layer226, and an IP layer 228. Such layers correspond to the layers 122–128,respectively, of the multimedia station 14 shown in the embodiment ofFIG. 3.

In the non-integrated configuration shown in the embodiments of FIGS.2–3, a conventional multimedia protocol stack was included in themultimedia station. That is, the behavior of the multimedia protocolsuch as H.323, in the non-integrated configuration is not aware of theexistence of an adaptation layer. The integrated configuration shown inthe embodiment of FIGS. 4–5 permits improved optimization andstreamlining by integrating the multimedia protocol stack with theadaptation layer. The stack is integrated with the adaptation layer inboth the control plane and user plane of FIGS. 4 and 5, respectively.

In the control plane shown in FIG. 4, the application signaling layer148 makes a determination that a special channel is required for thecommunication of real-time media. Responsive to such determination, arequest is forwarded to the requester 156 of the application layer 152.Thereby, need for a detector of the embodiment shown in FIG. 2 isobviated. Additionally, the adaptation layer 152 interfaces directly tothe application, above the TCP and IP layers 154 and 158. In contrast,in the non-integrated configuration shown in FIG. 2, the TCP and IPlayers are formed able the adaptation layer.

Also, in the user plane shown in FIG. 5, real-time media generated atthe station 12 is sent directly to the special channel 214, therebybypassing RTP, UDP and IP layers required in the non-integratedconfiguration shown in FIG. 3, also eliminating the requirement of aconverter 112 of such non-integrated embodiment.

FIG. 6 illustrates exemplary signal formats formed during operation ofthe multimedia stations 12 and 14 shown in the embodiments of FIGS. 2–3and 4–5. An exemplary packet 288 of multimedia information is shown tobe generated for transmission to the multimedia station 14. The packetis formed of a header portion 292 here including an IP section, a UDPsection, and an RTP section. Appended to the header portion is a datapayload 296, such as voice data.

During operation of the embodiment of the present invention shown inFIGS. 2–3, the adaptation layer 54 is operable, amongst other things, toconvert the packet-formatted data, of which the packet 288 is exemplary,into a form amenable for transmission upon a special channel, that is, acircuit-switched channel or the like, of the radio communication system.Once converted, the data payload 296 is transmitted upon the specialchannel, as indicated in the center section of the Figure. Once receivedat the access network infrastructure 34, the data is reconverted intopacket form as the packet 298. As illustrated, the packet 298corresponds to the packet 288.

FIG. 7 also represents the radio communication system 10 of theembodiment shown in FIGS. 2, 3, 4 and 5. Here, the networkinfrastructure is shown to include two access network infrastructures302 and 304 positioned, for example, to be associated with separate,spaced-apart base stations of a cellular communication network. TheFigure is illustrative of the ability, through operation of anembodiment of the present invention, to communicate multimediainformation between two mobile multimedia stations 12.

The multimedia stations 12 are operable in control and user planesanalogous to that described with respect to FIGS. 2, 3, 4 and 5 above.And, two access network infrastructures 34 are shown in the Figure, eachoperable relative to the stations 12 in manners described with respectto FIGS. 2, 3, 4 and 5 above. The separate access networkinfrastructures are coupled together by way of an IP backbone 78.

FIG. 8 illustrates a communication system 10 of a further embodiment ofthe present invention. In this implementation, multi-media informationis communicated between two sources and sinks, here sources/sinks 312and 313 of multi-media information. While, in the exemplaryimplementation, portions of the communication links formed between thesources/sinks 312 and 313 are formed of special channels formed of radiolinks 314–316, in other implementations, the communication link isformed in other manners, such as by way of wireline connections.

For purposes of defining operation of an embodiment of the presentinvention, the communication path formed between the sources/sinks ofmulti-media information 312 and 313 include IP networks 318, 322, and324. In conventional manner, multimedia data is communicated throughsuch IP networks by formatting the data in discrete packets, such aswith the RTP, UDP, and IP headers and formatting information, asdescribed above.

Communication system 10 is here shown to include a plurality of adaptors328 which are operable to adapt the packet data, formatted in theformatted form into a spectrally-efficient form for communication uponthe communication links 314–316 and to convert the media, oncetransmitted in the spectrally-efficient form into packetized form forcommunication over a respective IP network 318, 322, or 324.

The communication system 10 provides for 2-way communication of themulti-media information between the sources/sinks 312 and 313. Each ofthe adaptors 328, therefore, include an upstream adaptor portion 332 anda downstream adaptor portion 334. The upstream adaptor is defined as thedevice located on the same side of the radio link as the multimediasource, while the downstream adaptor is located on the same side of theradio link as the multimedia sink. The upstream adaptor portions of eachof the adaptors are operable to detect when real-time multi-media is tobe communicated upon a communication link and to request the allocationof a special channel upon the communication link to effectuate thecommunication of the real-time multi-media information thereto. Suchoperation is analogous to the operation of the adaptation layer 54described previously with respect to operation of the embodiment shownin FIG. 2. And, the upstream adaptor portions 332 are further operableto convert the packet-formatted multi-media information into spectrallyefficient form for transmission upon the special channel, once assigned.Such operation of the upstream adaptor is analogous to the operation ofthe adaptation layer 54 shown in the embodiment of FIG. 3. That is tosay, the upstream adaptor removes the RTP, UDP and IP headers

The downstream adaptor portions 334 of each of the adaptors 328 areoperable to detect reception of the multi-media information transmittedin the spectrally-efficient form upon a special channel upon acommunication link and to convert such communication into packet-dataform, all as described with respect to the operation of portions of theaccess network infrastructure shown in FIGS. 2–3. The downstream adaptoris operable to regenerate IP, UDP and RTP headers. The values of the UDPand IP fields do not change during a call, so their values need to besent by the upstream adaptor across the communications link (e.g., radiolink) to the downstream adaptor only when the detector detects areal-time media logical channel setup. The downstream adaptor thenmemorizes these values. For the RTP field, the downstream adaptor mustbe able to derive the correct current time stamps and sequence numbers.If the special channel is such that real-time media is received by thedownstream adaptor in a predictable manner, i.e., at a constant rate,the downstream adaptor is able to derive the running values of the RTPtime stamp and sequence numbers just by maintaining a local clock thatincrements monotonically and linearly in time. The initial time stampvalue and sampling rate can be sent by the upstream adaptor when thedetector derives the values from monitoring the application signaling.If the sampling rate were to subsequently change, the upstream adaptordetects it from the application signaling and updates the downstreamadaptor with the new sampling rate value.

In operation of the exemplary implementation shown in FIG. 8,multi-media information sourced at the multi-media information source312 is formatted into packets of data thereat and then communicated uponthe IP network 318 and delivered to the upstream adaptor portion 332 ofthe adaptor 328 connected to the IP network 318. The upstream adaptorportion 332 requests allocation of a special channel upon thecommunication link 314–316, and the portion 332 converts the packets ofdata into spectrally-efficient form for communication upon the specialchannel. A downstream adaptor portion 334 of the adaptor 329 coupled tothe IP network 322 reformats the multimedia information received thereatto permit its communication through the IP network 322 to an upstreamadaptor portion 332 of the adaptor 330 coupled to the IP network 322.Such upstream adaptor portion requests a special channel upon asubsequent communication link 314–316 and converts the packetized datainto spectrally-efficient form for communication thereon. Adaptor 331connected to the IP network 324 includes a downstream adaptor portion334 operable to reconvert the information into packetized form forcommunication through the IP network 324, thereafter to be delivered atthe multi-media source 313.

Multi-media information sourced at the source 313 is communicated to themulti-media source 312 in analogous but reverse manner. It shouldfurther he noted that any number of adaptor-communication link chainscan be concatenated together as necessary to interconnect multi-mediasending and receiving stations.

FIG. 9 illustrates a method shown generally at 412, of an embodiment ofthe present invention. The method communicates multimedia informationbetween a first communication station and a second communication stationof a radio communication system. First, and as indicated by the block414, the multimedia information is provided in packet-data form to thefirst communication station. Then, and as indicated by the block 416,control plane information associated with the multimedia information isdetected.

Then, as indicated by the block 418, allocation of a special channeldefined upon a radio-link between the first communication station andthe second communication station is requested. Then, and as indicated bythe block 422, the multimedia information is converted into a radio-linkformat, amenable for transmission upon the special channel. And, asindicated by the block 424, the multimedia information is transmittedupon the special channel to the second communication station. Thereby,through of operation of an embodiment of the present invention, a manneris provided by which to efficiently transmit multimedia information,generated pursuant to a multimedia protocol using RTP such as H.232 upona radio-link, such as that formed in a cellular communication system.The multimedia information is converted into a form amenable fortransmission upon the radio-link in a spectrally-efficient manner.

A fixed multimedia station sends and receives multimedia information inpacket data format, in accordance with H.323 or another protocol withsimilar concepts of logical channels. An access network infrastructureis provided so that the mobile multimedia station can send and receivemultimedia information in a format more adapted to the radio link. Theaccess network infrastructure takes care of the necessary conversion sothat seen from the entity corresponding with the mobile multimediastation, the mobile multimedia station plus access networkinfrastructure combination behaves like a fixed multimedia station. Thevarious entities on the communication path are mobile multimediastation—cellular infrastructure which contains the access networkinfrastructure—IP network—fixed multimedia station. An embodiment of thepresent invention also applies to the case of mobile multimedia stationto mobile multimedia station communication, in which case the entitieson the path are: first mobile multimedia station—cellularinfrastructure, which contains the access network infrastructureassociated with the first station—IP network—cellular infrastructurewhich contains the access network infrastructure associated with thesecond station—second mobile multimedia station.

The previous descriptions are of preferred examples for implementing theinvention, and the scope of the invention should not necessarily belimited by this description. The scope of the present invention isdefined by the following claims:

1. Apparatus for a radio communication system having a wireless gateway,the radio communication system operable to communicate multimediainformation with a first multimedia device and a second multimediadevice, for providing the multimedia information transmitted by thefirst multimedia device upon a special channel in radio-link format tothe second multimedia device, said apparatus comprising: a real-timemedia source at which the multimedia information is sourced; a requestercoupled to said real-time media source to receive indications of whenthe multimedia information is to be communicated by the first multimediadevice, said requester for requesting allocation of the special channelupon which to communicate the real-time media; a control planeinformation generator coupled to receive indications of the multimediainformation, said control plane information generator for generatingcontrol plane information, the control plane information controlling amanner by which to provide the multimedia information, once convertedinto packet-data form, to the second multimedia device; and a formatconverter coupled to receive indications of the multimedia informationin the radio-link format, said format converter for converting themultimedia information into the packet-data form, the multimediainformation, once converted into the packet-data form provided to thesecond multimedia device in the manner determined by the control planeinformation.
 2. The apparatus of claim 1 wherein said requester requeststhe allocation of the special channel with said control planeinformation generator.
 3. The apparatus of claim 2 wherein said controlplane information generator comprises a real-time manager, saidreal-time manager further for exchanging signaling with said requesterpursuant to the requests for the allocation of the special channel. 4.The apparatus of claim 3 wherein the first multimedia device is definedin terms of logical layers, wherein said real-time media source isformed at a first logical layer and said requester is formed at a secondlogical layer, the first logical layer of a higher logical-layer levelthan the second logical layer.
 5. The apparatus of claim 4 wherein thefirst logical layer comprises an application signaling layer.
 6. Theapparatus of claim 5 wherein the second logical layer comprises anadaptation layer.
 7. The apparatus of claim 6 further comprising a thirdlogical layer, the third logical layer of a lower logical-layer levelthan the second logical layer.
 8. The apparatus of claim 7 wherein thethird logical layer comprises a bearer signaling layer.
 9. Apparatus fora radio communication system having a wireless gateway, the radiocommunication system operable to communicate multimedia informationbetween a first multimedia device and a second multimedia device, forproviding the multimedia information transmitted by the first multimediadevice upon a special channel in radio-link format to the secondmultimedia device, said wireless gateway comprising: a real-time mediasource at which the multimedia information is sourced; a requestercoupled to said real-time media source to receive indications of whenthe multimedia information is to be communicated by the first multimediadevice, said requester for requesting with said control planeinformation generator allocation of the special channel upon which tocommunicate the real-time media; a control plane information generatorcoupled to receive indications of the multimedia information, saidcontrol plane information generator for generating control planeinformation, the control plane information controlling a manner by whichto provide the multimedia information, once converted into packet dataform, to the second multimedia device; and a format converter coupled toreceive indications of the multimedia information in the radio-linkformat, said format converter for converting the multimedia informationinto the packet-data form, the multimedia information, once convertedinto the packet-data form provided to the second multimedia device inthe manner determined by the control plane information.
 10. The wirelessgateway of claim 9 wherein said control plane information generatorcomprises a real-time manager, said real-time manager further forexchanging signaling with said requester pursuant to the requests forthe allocation of the special channel.
 11. The wireless gateway of claim10 wherein the first multimedia device is defined in terms of logicallayers, wherein said real-time media source is formed at a first logicallayer and said requester is formed at a second logical layer, the firstlogical layer of a higher logical-layer level than the second logicallayer.